Re: [Qemu-devel] [PATCH 2/6] serial: reinstate watch after migration

[Paolo Bonzini]

On 22/06/2016 17:05, Dr. David Alan Gilbert wrote:
> * Paolo Bonzini (address@hidden) wrote:
>> Otherwise, a serial port can get stuck if it is migrated while flow control
>> is in effect.
>>
>> Signed-off-by: Paolo Bonzini <address@hidden>
>> ---
>>  hw/char/serial.c         | 16 ++++++++++++++--
>>  include/hw/char/serial.h |  1 +
>>  2 files changed, 15 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/char/serial.c b/hw/char/serial.c
>> index e65e9e0..6f0a49e 100644
>> --- a/hw/char/serial.c
>> +++ b/hw/char/serial.c
>> @@ -639,8 +639,20 @@ static int serial_post_load(void *opaque, int 
>> version_id)
>>      if (s->thr_ipending == -1) {
>>          s->thr_ipending = ((s->iir & UART_IIR_ID) == UART_IIR_THRI);
>>      }
>> -    if (s->tsr_retry > MAX_XMIT_RETRY) {
>> -        s->tsr_retry = MAX_XMIT_RETRY;
> 
> Why remove the check you just added?

Because I'm dumb. :)

>> +
>> +    if (s->tsr_retry > 0) {
>> +        /* tsr_retry > 0 implies LSR.TEMT = 0 (transmitter not empty).  */
>> +        if (s->lsr & UART_LSR_TEMT) {
>> +            return -1;
>> +        }
>> +
>> +        assert(s->watch_tag == 0);
>> +        s->watch_tag = qemu_chr_fe_add_watch(s->chr, G_IO_OUT|G_IO_HUP, 
>> serial_xmit, s);
>> +    } else {
>> +        /* tsr_retry == 0 implies LSR.TEMT = 1 (transmitter empty).  */
>> +        if (!(s->lsr & UART_LSR_TEMT)) {
>> +            return -1;
> 
> If you're failing migration (-1) then please error_report to say why
> so when someone hits it I can immediately see why.

Ok, something like

    error_report("inconsistent state in serial device");

?

Paolo